diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index d5d7435..a5549fc 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -2472,7 +2472,7 @@
 
     releaseObjects();
 
-    if (data) {
+    if (data || desired == 0) {
         LOG_ALLOC("Parcel %p: restart from %zu to %zu capacity", this, mDataCapacity, desired);
         pthread_mutex_lock(&gParcelGlobalAllocSizeLock);
         gParcelGlobalAllocSize += desired;
diff --git a/services/sensorservice/SensorDevice.cpp b/services/sensorservice/SensorDevice.cpp
index 8a282e2..e355594 100644
--- a/services/sensorservice/SensorDevice.cpp
+++ b/services/sensorservice/SensorDevice.cpp
@@ -153,12 +153,18 @@
                                     SensorDeviceUtils::defaultResolutionForType(sensor.type);
                         }
 
-                        double promotedResolution = sensor.resolution;
-                        double promotedMaxRange = sensor.maxRange;
-                        if (fmod(promotedMaxRange, promotedResolution) != 0) {
-                            ALOGW("%s's max range %f is not a multiple of the resolution %f",
-                                    sensor.name, sensor.maxRange, sensor.resolution);
-                            SensorDeviceUtils::quantizeValue(&sensor.maxRange, promotedResolution);
+                        // Some sensors don't have a default resolution and will be left at 0.
+                        // Don't crash in this case since CTS will verify that devices don't go to
+                        // production with a resolution of 0.
+                        if (sensor.resolution != 0) {
+                            double promotedResolution = sensor.resolution;
+                            double promotedMaxRange = sensor.maxRange;
+                            if (fmod(promotedMaxRange, promotedResolution) != 0) {
+                                ALOGW("%s's max range %f is not a multiple of the resolution %f",
+                                        sensor.name, sensor.maxRange, sensor.resolution);
+                                SensorDeviceUtils::quantizeValue(
+                                        &sensor.maxRange, promotedResolution);
+                            }
                         }
                     }
 
diff --git a/services/surfaceflinger/BufferQueueLayer.cpp b/services/surfaceflinger/BufferQueueLayer.cpp
index 07be791..6e4235e 100644
--- a/services/surfaceflinger/BufferQueueLayer.cpp
+++ b/services/surfaceflinger/BufferQueueLayer.cpp
@@ -324,9 +324,6 @@
         }
 
         uint64_t bufferID = mQueueItems[0].mGraphicBuffer->getId();
-        mFlinger->mFrameTracer->traceFence(layerId, bufferID, currentFrameNumber,
-                                           mQueueItems[0].mFenceTime,
-                                           FrameTracer::FrameEvent::ACQUIRE_FENCE);
         mFlinger->mTimeStats->setLatchTime(layerId, currentFrameNumber, latchTime);
         mFlinger->mFrameTracer->traceTimestamp(layerId, bufferID, currentFrameNumber, latchTime,
                                                FrameTracer::FrameEvent::LATCH);
@@ -393,8 +390,12 @@
 
 void BufferQueueLayer::onFrameAvailable(const BufferItem& item) {
     const int32_t layerId = getSequence();
-    mFlinger->mFrameTracer->traceTimestamp(layerId, item.mGraphicBuffer->getId(), item.mFrameNumber,
-                                           systemTime(), FrameTracer::FrameEvent::QUEUE);
+    const uint64_t bufferId = item.mGraphicBuffer->getId();
+    mFlinger->mFrameTracer->traceTimestamp(layerId, bufferId, item.mFrameNumber, systemTime(),
+                                           FrameTracer::FrameEvent::QUEUE);
+    mFlinger->mFrameTracer->traceFence(layerId, bufferId, item.mFrameNumber,
+                                       std::make_shared<FenceTime>(item.mFence),
+                                       FrameTracer::FrameEvent::ACQUIRE_FENCE);
 
     ATRACE_CALL();
     // Add this buffer from our internal queue tracker
@@ -460,8 +461,12 @@
     }
 
     const int32_t layerId = getSequence();
-    mFlinger->mFrameTracer->traceTimestamp(layerId, item.mGraphicBuffer->getId(), item.mFrameNumber,
-                                           systemTime(), FrameTracer::FrameEvent::QUEUE);
+    const uint64_t bufferId = item.mGraphicBuffer->getId();
+    mFlinger->mFrameTracer->traceTimestamp(layerId, bufferId, item.mFrameNumber, systemTime(),
+                                           FrameTracer::FrameEvent::QUEUE);
+    mFlinger->mFrameTracer->traceFence(layerId, bufferId, item.mFrameNumber,
+                                       std::make_shared<FenceTime>(item.mFence),
+                                       FrameTracer::FrameEvent::ACQUIRE_FENCE);
     mConsumer->onBufferAvailable(item);
 }
 
diff --git a/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.cpp b/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.cpp
index a596bce..2a6fd05 100644
--- a/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.cpp
+++ b/services/surfaceflinger/Scheduler/VSyncDispatchTimerQueue.cpp
@@ -243,7 +243,8 @@
     std::vector<Invocation> invocations;
     {
         std::lock_guard<decltype(mMutex)> lk(mMutex);
-        mLastTimerCallback = mTimeKeeper->now();
+        auto const now = mTimeKeeper->now();
+        mLastTimerCallback = now;
         for (auto it = mCallbacks.begin(); it != mCallbacks.end(); it++) {
             auto& callback = it->second;
             auto const wakeupTime = callback->wakeupTime();
@@ -251,7 +252,8 @@
                 continue;
             }
 
-            if (*wakeupTime < mIntendedWakeupTime + mTimerSlack) {
+            auto const lagAllowance = std::max(now - mIntendedWakeupTime, static_cast<nsecs_t>(0));
+            if (*wakeupTime < mIntendedWakeupTime + mTimerSlack + lagAllowance) {
                 callback->executing();
                 invocations.emplace_back(
                         Invocation{callback, *callback->lastExecutedVsyncTarget(), *wakeupTime});
diff --git a/services/surfaceflinger/Scheduler/VSyncPredictor.cpp b/services/surfaceflinger/Scheduler/VSyncPredictor.cpp
index ab5773d..61f3fbb 100644
--- a/services/surfaceflinger/Scheduler/VSyncPredictor.cpp
+++ b/services/surfaceflinger/Scheduler/VSyncPredictor.cpp
@@ -255,21 +255,9 @@
     }
 }
 
-bool VSyncPredictor::needsMoreSamples(nsecs_t now) const {
-    using namespace std::literals::chrono_literals;
+bool VSyncPredictor::needsMoreSamples() const {
     std::lock_guard<std::mutex> lk(mMutex);
-    bool needsMoreSamples = true;
-    if (mTimestamps.size() >= kMinimumSamplesForPrediction) {
-        nsecs_t constexpr aLongTime =
-                std::chrono::duration_cast<std::chrono::nanoseconds>(500ms).count();
-        if (!(mLastTimestampIndex < 0 || mTimestamps.empty())) {
-            auto const lastTimestamp = mTimestamps[mLastTimestampIndex];
-            needsMoreSamples = !((lastTimestamp + aLongTime) > now);
-        }
-    }
-
-    ATRACE_INT("VSP-moreSamples", needsMoreSamples);
-    return needsMoreSamples;
+    return mTimestamps.size() < kMinimumSamplesForPrediction;
 }
 
 void VSyncPredictor::resetModel() {
diff --git a/services/surfaceflinger/Scheduler/VSyncPredictor.h b/services/surfaceflinger/Scheduler/VSyncPredictor.h
index 3ca878d..5f3c418 100644
--- a/services/surfaceflinger/Scheduler/VSyncPredictor.h
+++ b/services/surfaceflinger/Scheduler/VSyncPredictor.h
@@ -52,11 +52,10 @@
      */
     void setPeriod(nsecs_t period) final;
 
-    /* Query if the model is in need of more samples to make a prediction at timePoint.
-     * \param [in] timePoint    The timePoint to inquire of.
+    /* Query if the model is in need of more samples to make a prediction.
      * \return  True, if model would benefit from more samples, False if not.
      */
-    bool needsMoreSamples(nsecs_t timePoint) const;
+    bool needsMoreSamples() const final;
 
     std::tuple<nsecs_t /* slope */, nsecs_t /* intercept */> getVSyncPredictionModel() const;
 
diff --git a/services/surfaceflinger/Scheduler/VSyncReactor.cpp b/services/surfaceflinger/Scheduler/VSyncReactor.cpp
index c743de0..efa8bab 100644
--- a/services/surfaceflinger/Scheduler/VSyncReactor.cpp
+++ b/services/surfaceflinger/Scheduler/VSyncReactor.cpp
@@ -233,6 +233,7 @@
 }
 
 void VSyncReactor::startPeriodTransition(nsecs_t newPeriod) {
+    ATRACE_CALL();
     mPeriodConfirmationInProgress = true;
     mPeriodTransitioningTo = newPeriod;
     mMoreSamplesNeeded = true;
@@ -240,8 +241,7 @@
 }
 
 void VSyncReactor::endPeriodTransition() {
-    setIgnorePresentFencesInternal(false);
-    mMoreSamplesNeeded = false;
+    ATRACE_CALL();
     mPeriodTransitioningTo.reset();
     mPeriodConfirmationInProgress = false;
     mLastHwVsync.reset();
@@ -254,6 +254,8 @@
 
     if (!mSupportKernelIdleTimer && period == getPeriod()) {
         endPeriodTransition();
+        setIgnorePresentFencesInternal(false);
+        mMoreSamplesNeeded = false;
     } else {
         startPeriodTransition(period);
     }
@@ -303,6 +305,7 @@
 
     std::lock_guard<std::mutex> lk(mMutex);
     if (periodConfirmed(timestamp, hwcVsyncPeriod)) {
+        ATRACE_NAME("VSR: period confirmed");
         if (mPeriodTransitioningTo) {
             mTracker->setPeriod(*mPeriodTransitioningTo);
             for (auto& entry : mCallbacks) {
@@ -310,17 +313,29 @@
             }
             *periodFlushed = true;
         }
+
+        if (mLastHwVsync) {
+            mTracker->addVsyncTimestamp(*mLastHwVsync);
+        }
+        mTracker->addVsyncTimestamp(timestamp);
+
         endPeriodTransition();
+        mMoreSamplesNeeded = mTracker->needsMoreSamples();
     } else if (mPeriodConfirmationInProgress) {
+        ATRACE_NAME("VSR: still confirming period");
         mLastHwVsync = timestamp;
         mMoreSamplesNeeded = true;
         *periodFlushed = false;
     } else {
-        mMoreSamplesNeeded = false;
+        ATRACE_NAME("VSR: adding sample");
         *periodFlushed = false;
+        mTracker->addVsyncTimestamp(timestamp);
+        mMoreSamplesNeeded = mTracker->needsMoreSamples();
     }
 
-    mTracker->addVsyncTimestamp(timestamp);
+    if (!mMoreSamplesNeeded) {
+        setIgnorePresentFencesInternal(false);
+    }
     return mMoreSamplesNeeded;
 }
 
diff --git a/services/surfaceflinger/Scheduler/VSyncTracker.h b/services/surfaceflinger/Scheduler/VSyncTracker.h
index 05a6fc3..107c540 100644
--- a/services/surfaceflinger/Scheduler/VSyncTracker.h
+++ b/services/surfaceflinger/Scheduler/VSyncTracker.h
@@ -66,6 +66,8 @@
     /* Inform the tracker that the samples it has are not accurate for prediction. */
     virtual void resetModel() = 0;
 
+    virtual bool needsMoreSamples() const = 0;
+
     virtual void dump(std::string& result) const = 0;
 
 protected:
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 0ac3d32..148749e 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1566,7 +1566,7 @@
     mEventQueue->refresh();
 }
 
-nsecs_t SurfaceFlinger::getVsyncPeriod() const {
+nsecs_t SurfaceFlinger::getVsyncPeriodFromHWC() const {
     const auto displayId = getInternalDisplayIdLocked();
     if (!displayId || !getHwComposer().isConnected(*displayId)) {
         return 0;
@@ -1773,7 +1773,7 @@
     setPowerModeInternal(display, currentDisplayPowerMode);
 
     // Reset the timing values to account for the period of the swapped in HWC
-    const nsecs_t vsyncPeriod = getVsyncPeriod();
+    const nsecs_t vsyncPeriod = mRefreshRateConfigs->getCurrentRefreshRate().getVsyncPeriod();
     mAnimFrameTracker.setDisplayRefreshPeriod(vsyncPeriod);
 
     // The present fences returned from vr_hwc are not an accurate
@@ -4192,8 +4192,7 @@
                         {});
 
     setPowerModeInternal(display, hal::PowerMode::ON);
-
-    const nsecs_t vsyncPeriod = getVsyncPeriod();
+    const nsecs_t vsyncPeriod = mRefreshRateConfigs->getCurrentRefreshRate().getVsyncPeriod();
     mAnimFrameTracker.setDisplayRefreshPeriod(vsyncPeriod);
 
     // Use phase of 0 since phase is not known.
@@ -4228,7 +4227,7 @@
     if (mInterceptor->isEnabled()) {
         mInterceptor->savePowerModeUpdate(display->getSequenceId(), static_cast<int32_t>(mode));
     }
-
+    const auto vsyncPeriod = mRefreshRateConfigs->getCurrentRefreshRate().getVsyncPeriod();
     if (currentMode == hal::PowerMode::OFF) {
         if (SurfaceFlinger::setSchedFifo(true) != NO_ERROR) {
             ALOGW("Couldn't set SCHED_FIFO on display on: %s\n", strerror(errno));
@@ -4237,7 +4236,7 @@
         if (display->isPrimary() && mode != hal::PowerMode::DOZE_SUSPEND) {
             getHwComposer().setVsyncEnabled(*displayId, mHWCVsyncPendingState);
             mScheduler->onScreenAcquired(mAppConnectionHandle);
-            mScheduler->resyncToHardwareVsync(true, getVsyncPeriod());
+            mScheduler->resyncToHardwareVsync(true, vsyncPeriod);
         }
 
         mVisibleRegionsDirty = true;
@@ -4264,7 +4263,7 @@
         getHwComposer().setPowerMode(*displayId, mode);
         if (display->isPrimary() && currentMode == hal::PowerMode::DOZE_SUSPEND) {
             mScheduler->onScreenAcquired(mAppConnectionHandle);
-            mScheduler->resyncToHardwareVsync(true, getVsyncPeriod());
+            mScheduler->resyncToHardwareVsync(true, vsyncPeriod);
         }
     } else if (mode == hal::PowerMode::DOZE_SUSPEND) {
         // Leave display going to doze
@@ -4377,7 +4376,7 @@
 }
 
 void SurfaceFlinger::dumpStatsLocked(const DumpArgs& args, std::string& result) const {
-    StringAppendF(&result, "%" PRId64 "\n", getVsyncPeriod());
+    StringAppendF(&result, "%" PRId64 "\n", getVsyncPeriodFromHWC());
 
     if (args.size() > 1) {
         const auto name = String8(args[1]);
@@ -4442,7 +4441,7 @@
     mPhaseConfiguration->dump(result);
     StringAppendF(&result,
                   "      present offset: %9" PRId64 " ns\t     VSYNC period: %9" PRId64 " ns\n\n",
-                  dispSyncPresentTimeOffset, getVsyncPeriod());
+                  dispSyncPresentTimeOffset, getVsyncPeriodFromHWC());
 
     scheduler::RefreshRateConfigs::Policy policy = mRefreshRateConfigs->getDisplayManagerPolicy();
     StringAppendF(&result,
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index ccaeb2d..c727574 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -852,7 +852,7 @@
     /* ------------------------------------------------------------------------
      * VSync
      */
-    nsecs_t getVsyncPeriod() const REQUIRES(mStateLock);
+    nsecs_t getVsyncPeriodFromHWC() const REQUIRES(mStateLock);
 
     // Sets the refresh rate by switching active configs, if they are available for
     // the desired refresh rate.
diff --git a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
index ce5f35c..06bdcdc 100644
--- a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
@@ -85,7 +85,7 @@
 using HotplugEvent = TestableSurfaceFlinger::HotplugEvent;
 using HWC2Display = TestableSurfaceFlinger::HWC2Display;
 
-constexpr int32_t DEFAULT_REFRESH_RATE = 16'666'666;
+constexpr int32_t DEFAULT_REFRESH_RATE = 16'666'667;
 constexpr int32_t DEFAULT_DPI = 320;
 constexpr int DEFAULT_VIRTUAL_DISPLAY_SURFACE_FORMAT = HAL_PIXEL_FORMAT_RGB_565;
 
diff --git a/services/surfaceflinger/tests/unittests/VSyncDispatchRealtimeTest.cpp b/services/surfaceflinger/tests/unittests/VSyncDispatchRealtimeTest.cpp
index be49ef3..c2a7752 100644
--- a/services/surfaceflinger/tests/unittests/VSyncDispatchRealtimeTest.cpp
+++ b/services/surfaceflinger/tests/unittests/VSyncDispatchRealtimeTest.cpp
@@ -51,6 +51,7 @@
 
     void setPeriod(nsecs_t) final {}
     void resetModel() final {}
+    bool needsMoreSamples() const final { return false; }
     void dump(std::string&) const final {}
 
 private:
@@ -86,6 +87,7 @@
 
     void setPeriod(nsecs_t) final {}
     void resetModel() final {}
+    bool needsMoreSamples() const final { return false; }
     void dump(std::string&) const final {}
 
 private:
diff --git a/services/surfaceflinger/tests/unittests/VSyncDispatchTimerQueueTest.cpp b/services/surfaceflinger/tests/unittests/VSyncDispatchTimerQueueTest.cpp
index d940dc5..373f6a5 100644
--- a/services/surfaceflinger/tests/unittests/VSyncDispatchTimerQueueTest.cpp
+++ b/services/surfaceflinger/tests/unittests/VSyncDispatchTimerQueueTest.cpp
@@ -47,6 +47,7 @@
     MOCK_CONST_METHOD0(currentPeriod, nsecs_t());
     MOCK_METHOD1(setPeriod, void(nsecs_t));
     MOCK_METHOD0(resetModel, void());
+    MOCK_CONST_METHOD0(needsMoreSamples, bool());
     MOCK_CONST_METHOD1(dump, void(std::string&));
 
     nsecs_t nextVSyncTime(nsecs_t timePoint) const {
@@ -115,11 +116,15 @@
 
     operator VSyncDispatch::CallbackToken() const { return mToken; }
 
-    void counter(nsecs_t time, nsecs_t) { mCalls.push_back(time); }
+    void counter(nsecs_t time, nsecs_t wakeup_time) {
+        mCalls.push_back(time);
+        mWakeupTime.push_back(wakeup_time);
+    }
 
     VSyncDispatch& mDispatch;
     VSyncDispatch::CallbackToken mToken;
     std::vector<nsecs_t> mCalls;
+    std::vector<nsecs_t> mWakeupTime;
 };
 
 class PausingCallback {
@@ -747,6 +752,31 @@
     EXPECT_THAT(cb2.mCalls.size(), Eq(1));
 }
 
+TEST_F(VSyncDispatchTimerQueueTest, laggedTimerGroupsCallbacksWithinLag) {
+    CountingCallback cb1(mDispatch);
+    CountingCallback cb2(mDispatch);
+
+    Sequence seq;
+    EXPECT_CALL(mStubTracker, nextAnticipatedVSyncTimeFrom(1000))
+            .InSequence(seq)
+            .WillOnce(Return(1000));
+    EXPECT_CALL(mMockClock, alarmIn(_, 600)).InSequence(seq);
+    EXPECT_CALL(mStubTracker, nextAnticipatedVSyncTimeFrom(1000))
+            .InSequence(seq)
+            .WillOnce(Return(1000));
+
+    EXPECT_EQ(mDispatch.schedule(cb1, 400, 1000), ScheduleResult::Scheduled);
+    EXPECT_EQ(mDispatch.schedule(cb2, 390, 1000), ScheduleResult::Scheduled);
+
+    mMockClock.setLag(100);
+    mMockClock.advanceBy(700);
+
+    ASSERT_THAT(cb1.mWakeupTime.size(), Eq(1));
+    EXPECT_THAT(cb1.mWakeupTime[0], Eq(600));
+    ASSERT_THAT(cb2.mWakeupTime.size(), Eq(1));
+    EXPECT_THAT(cb2.mWakeupTime[0], Eq(610));
+}
+
 class VSyncDispatchTimerQueueEntryTest : public testing::Test {
 protected:
     nsecs_t const mPeriod = 1000;
diff --git a/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp b/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp
index fc39235..d4cd11d 100644
--- a/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp
+++ b/services/surfaceflinger/tests/unittests/VSyncPredictorTest.cpp
@@ -73,27 +73,27 @@
 
 TEST_F(VSyncPredictorTest, reportsSamplesNeededWhenHasNoDataPoints) {
     for (auto i = 0u; i < kMinimumSamplesForPrediction; i++) {
-        EXPECT_TRUE(tracker.needsMoreSamples(mNow += mPeriod));
-        tracker.addVsyncTimestamp(mNow);
+        EXPECT_TRUE(tracker.needsMoreSamples());
+        tracker.addVsyncTimestamp(mNow += mPeriod);
     }
-    EXPECT_FALSE(tracker.needsMoreSamples(mNow));
+    EXPECT_FALSE(tracker.needsMoreSamples());
 }
 
 TEST_F(VSyncPredictorTest, reportsSamplesNeededAfterExplicitRateChange) {
     for (auto i = 0u; i < kMinimumSamplesForPrediction; i++) {
         tracker.addVsyncTimestamp(mNow += mPeriod);
     }
-    EXPECT_FALSE(tracker.needsMoreSamples(mNow));
+    EXPECT_FALSE(tracker.needsMoreSamples());
 
     auto const changedPeriod = mPeriod * 2;
     tracker.setPeriod(changedPeriod);
-    EXPECT_TRUE(tracker.needsMoreSamples(mNow));
+    EXPECT_TRUE(tracker.needsMoreSamples());
 
     for (auto i = 0u; i < kMinimumSamplesForPrediction; i++) {
-        EXPECT_TRUE(tracker.needsMoreSamples(mNow += changedPeriod));
-        tracker.addVsyncTimestamp(mNow);
+        EXPECT_TRUE(tracker.needsMoreSamples());
+        tracker.addVsyncTimestamp(mNow += changedPeriod);
     }
-    EXPECT_FALSE(tracker.needsMoreSamples(mNow));
+    EXPECT_FALSE(tracker.needsMoreSamples());
 }
 
 TEST_F(VSyncPredictorTest, transitionsToModelledPointsAfterSynthetic) {
@@ -320,20 +320,6 @@
     EXPECT_THAT(intercept, Eq(0));
 }
 
-TEST_F(VSyncPredictorTest, willBecomeInaccurateAfterA_longTimeWithNoSamples) {
-    auto const simulatedVsyncs = generateVsyncTimestamps(kMinimumSamplesForPrediction, mPeriod, 0);
-
-    for (auto const& timestamp : simulatedVsyncs) {
-        tracker.addVsyncTimestamp(timestamp);
-    }
-    auto const mNow = *simulatedVsyncs.rbegin();
-    EXPECT_FALSE(tracker.needsMoreSamples(mNow));
-
-    // TODO: would be better to decay this as a result of the variance of the samples
-    static auto constexpr aLongTimeOut = 1000000000;
-    EXPECT_TRUE(tracker.needsMoreSamples(mNow + aLongTimeOut));
-}
-
 TEST_F(VSyncPredictorTest, idealModelPredictionsBeforeRegressionModelIsBuilt) {
     auto const simulatedVsyncs =
             generateVsyncTimestamps(kMinimumSamplesForPrediction + 1, mPeriod, 0);
@@ -443,7 +429,7 @@
         // When VsyncPredictor returns the period it means that it doesn't know how to predict and
         // it needs to get more samples
         if (slope == mPeriod && intercept == 0) {
-            EXPECT_TRUE(tracker.needsMoreSamples(now));
+            EXPECT_TRUE(tracker.needsMoreSamples());
         }
     }
 }
diff --git a/services/surfaceflinger/tests/unittests/VSyncReactorTest.cpp b/services/surfaceflinger/tests/unittests/VSyncReactorTest.cpp
index a972562..6856612 100644
--- a/services/surfaceflinger/tests/unittests/VSyncReactorTest.cpp
+++ b/services/surfaceflinger/tests/unittests/VSyncReactorTest.cpp
@@ -41,6 +41,7 @@
     MOCK_CONST_METHOD0(currentPeriod, nsecs_t());
     MOCK_METHOD1(setPeriod, void(nsecs_t));
     MOCK_METHOD0(resetModel, void());
+    MOCK_CONST_METHOD0(needsMoreSamples, bool());
     MOCK_CONST_METHOD1(dump, void(std::string&));
 };
 
@@ -57,6 +58,7 @@
     nsecs_t currentPeriod() const final { return mTracker->currentPeriod(); }
     void setPeriod(nsecs_t period) final { mTracker->setPeriod(period); }
     void resetModel() final { mTracker->resetModel(); }
+    bool needsMoreSamples() const final { return mTracker->needsMoreSamples(); }
     void dump(std::string& result) const final { mTracker->dump(result); }
 
 private:
@@ -455,6 +457,83 @@
     EXPECT_FALSE(mReactor.addPresentFence(generateSignalledFenceWithTime(0)));
 }
 
+TEST_F(VSyncReactorTest, hwVsyncIsRequestedForTracker) {
+    auto time = 0;
+    bool periodFlushed = false;
+    nsecs_t const newPeriod = 4000;
+    mReactor.setPeriod(newPeriod);
+
+    static auto constexpr numSamplesWithNewPeriod = 4;
+    Sequence seq;
+    EXPECT_CALL(*mMockTracker, needsMoreSamples())
+            .Times(numSamplesWithNewPeriod - 2)
+            .InSequence(seq)
+            .WillRepeatedly(Return(true));
+    EXPECT_CALL(*mMockTracker, needsMoreSamples())
+            .Times(1)
+            .InSequence(seq)
+            .WillRepeatedly(Return(false));
+    EXPECT_CALL(*mMockTracker, addVsyncTimestamp(_)).Times(numSamplesWithNewPeriod);
+
+    EXPECT_TRUE(mReactor.addResyncSample(time += period, std::nullopt, &periodFlushed));
+
+    EXPECT_TRUE(mReactor.addResyncSample(time += period, std::nullopt, &periodFlushed));
+    // confirmed period, but predictor wants numRequest samples. This one and prior are valid.
+    EXPECT_TRUE(mReactor.addResyncSample(time += newPeriod, std::nullopt, &periodFlushed));
+    EXPECT_TRUE(mReactor.addResyncSample(time += newPeriod, std::nullopt, &periodFlushed));
+    EXPECT_FALSE(mReactor.addResyncSample(time += newPeriod, std::nullopt, &periodFlushed));
+}
+
+TEST_F(VSyncReactorTest, hwVsyncturnsOffOnConfirmationWhenTrackerDoesntRequest) {
+    auto time = 0;
+    bool periodFlushed = false;
+    nsecs_t const newPeriod = 4000;
+    mReactor.setPeriod(newPeriod);
+
+    Sequence seq;
+    EXPECT_CALL(*mMockTracker, needsMoreSamples())
+            .Times(1)
+            .InSequence(seq)
+            .WillRepeatedly(Return(false));
+    EXPECT_CALL(*mMockTracker, addVsyncTimestamp(_)).Times(2);
+
+    EXPECT_TRUE(mReactor.addResyncSample(time += period, std::nullopt, &periodFlushed));
+    EXPECT_TRUE(mReactor.addResyncSample(time += period, std::nullopt, &periodFlushed));
+    EXPECT_FALSE(mReactor.addResyncSample(time += newPeriod, std::nullopt, &periodFlushed));
+}
+
+TEST_F(VSyncReactorTest, hwVsyncIsRequestedForTrackerMultiplePeriodChanges) {
+    auto time = 0;
+    bool periodFlushed = false;
+    nsecs_t const newPeriod1 = 4000;
+    nsecs_t const newPeriod2 = 7000;
+
+    mReactor.setPeriod(newPeriod1);
+
+    Sequence seq;
+    EXPECT_CALL(*mMockTracker, needsMoreSamples())
+            .Times(4)
+            .InSequence(seq)
+            .WillRepeatedly(Return(true));
+    EXPECT_CALL(*mMockTracker, needsMoreSamples())
+            .Times(1)
+            .InSequence(seq)
+            .WillRepeatedly(Return(false));
+    EXPECT_CALL(*mMockTracker, addVsyncTimestamp(_)).Times(7);
+
+    EXPECT_TRUE(mReactor.addResyncSample(time += period, std::nullopt, &periodFlushed));
+    EXPECT_TRUE(mReactor.addResyncSample(time += period, std::nullopt, &periodFlushed));
+    // confirmed period, but predictor wants numRequest samples. This one and prior are valid.
+    EXPECT_TRUE(mReactor.addResyncSample(time += newPeriod1, std::nullopt, &periodFlushed));
+    EXPECT_TRUE(mReactor.addResyncSample(time += newPeriod1, std::nullopt, &periodFlushed));
+
+    mReactor.setPeriod(newPeriod2);
+    EXPECT_TRUE(mReactor.addResyncSample(time += newPeriod1, std::nullopt, &periodFlushed));
+    EXPECT_TRUE(mReactor.addResyncSample(time += newPeriod2, std::nullopt, &periodFlushed));
+    EXPECT_TRUE(mReactor.addResyncSample(time += newPeriod2, std::nullopt, &periodFlushed));
+    EXPECT_FALSE(mReactor.addResyncSample(time += newPeriod2, std::nullopt, &periodFlushed));
+}
+
 static nsecs_t computeWorkload(nsecs_t period, nsecs_t phase) {
     return period - phase;
 }
@@ -648,7 +727,7 @@
 
 TEST_F(VSyncReactorTest, periodChangeWithGivenVsyncPeriod) {
     bool periodFlushed = true;
-    EXPECT_CALL(*mMockTracker, addVsyncTimestamp(_)).Times(3);
+    EXPECT_CALL(*mMockTracker, addVsyncTimestamp(_)).Times(2);
     mReactor.setIgnorePresentFences(true);
 
     nsecs_t const newPeriod = 5000;
@@ -672,7 +751,7 @@
                                     kPendingLimit, true /* supportKernelIdleTimer */);
 
     bool periodFlushed = true;
-    EXPECT_CALL(*mMockTracker, addVsyncTimestamp(_)).Times(5);
+    EXPECT_CALL(*mMockTracker, addVsyncTimestamp(_)).Times(4);
     idleReactor.setIgnorePresentFences(true);
 
     // First, set the same period, which should only be confirmed when we receive two